Yeah...Blonde is the one that drove MC's sister to her suicide. I'm guessing that subplot is like the thousands of blackmailing porn stories that are on the internet. Blonde got something to blackmail the sister and then repeatedly r**ed her until she couldn't take it anymore.
Maybe if MC did start to have sex with her, then blonde may have ended up in jail for assault. IDK. I have a feeling we'll figure out that subplot sooner or later.